/**
 * Copyright 2012 Brigham Young University
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *    http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package edu.byu.nlp.pipes;

import java.io.File;
import java.util.Iterator;

import com.google.common.base.Preconditions;
import com.google.common.collect.UnmodifiableIterator;

import edu.byu.nlp.io.AbstractIterable;

/**
 * @author rah67
 *
 */
public class DirectoryReader implements DataSource<String, String> {

	private final class ArrayIterator<T> extends UnmodifiableIterator<Instance<String, T>> {

		private final T[] files;
		private int i;

		private ArrayIterator(T[] files) {
			this.files = files;
			i = 0;
		}

		@Override
		public boolean hasNext() {
			return i < files.length;
		}

		@Override
		public Instance<String, T> next() {
			return new BasicInstance<String, T>(null, directory.toString(), files[i++]);
		}
	}

	private final class FilesIterable extends AbstractIterable<Instance<String, String>> {
		
		@Override
		public Iterator<Instance<String, String>> iterator() {
			return new ArrayIterator<String>(directory.list());
		}
	}

	private File directory;

	public DirectoryReader(File directory) {
		Preconditions.checkNotNull(directory);
		Preconditions.checkArgument(directory.isDirectory(), directory + " is not a directory");
		
		this.directory = directory;
	}

	/** {@inheritDoc} */
	@Override
	public Iterable<Instance<String, String>> getData() {
		return new FilesIterable();
	}

}
